Method and apparatus for making fabrics



April 1954 c. H. PLUMMER ET AL 2,676,363

METHOD AND APPARATUS FOR MAKING FABRICS File d Feb. 25, 1949 Tlcz l.

' INVENTORS: .C'HIPZES A6 @wwmw /V TPmsz 014 Patented Apr. 27 1954 UNITED STATES .TSET QFFICE METHOD AND APPARATUS FOR MAKING FABRICS Charles H. Plummcr, Neal Truslow, and John Frydryk, Springfield, Mass, assignors to Chicopee Manufacturing Corporation, a corporation of Massachusetts 9 Claims.

This invention relates to apparatus and methods for making non-woven fabric or cloth from various fibers.

Many people have long tried to make cloth without either spinning or weaving the fibers. This has usually been attempted by laying down a thin layer of fibers (cotton or rayon staple for example) and binding or cementing the fibers together to form a sheet. The fibers have usually been laid down by carding, which aligns the majority of the fibers lengthwise of the cloth and so forms a fabric having inadequate cross strength. It has also been proposed to suspend fibers in an air stream, then filter the fibers out on a screen to form a layer in which the fibers are arranged at random and thus to provide, after binding, a fabric which is more or less isotropic which means, as used here, having the same properties in all directions in the plane of the sheet. Such an isotropic fabrictheoretically has equal tensile strength or breaking strength lengthwise and crosswise. While this theoretical method of manufacture has been proposed, and while as heretofore proposed it might be used to make thick bats or laps, no one previous to this invention, as far as is known, has devised a method or apparatus which successfully produces uniform thin fabrics, nor has anyone made practical isotropic fabrics at commercially practical costs or rates of production.

The inherent difficulties of making such fabrics are especially marked in attempting to make uniform fabrics from the textile fibers, by which we mean fibers long enough to be spun and woven into cloth. And with the textile fibers the difficulty increases as the fiber length increases, so that with long fibers, such as inch and longer, it has been commercially impossible to make a uniform fabric. Further, the difficulty increases as the thickness of the attempted fabric decreases. For many purposes, especially in thin fabrics, it is desirable to use long fibers to increase the strength of the fabric.

One of the objects of the invention is to provide improved methods and improved apparatus for making a highly uniform substantially isotropic web from a wide variety of fibers and in a wide range of thickness. It is especially an object of the invention to make very thin webs, for example of the order of 100 grains per square yard, and to makesuch Webs of long staple fibers, inch and longer, inorder to provideadequate strength and durability and desirable hand. Another object is. to provide a simple and inexpensive machine which can be operated at high rates of produc-- tion and produc such webs inexpensively.

Other objects and advantages of the invention will be evident in the following description and in the accompanying drawings. In the drawings:

Fig. 1 is a diagrammatic vertical section on the line il of Fig. 2, of one form of apparatus for carrying out the invention;

Fig. 2 is a plan view of Fig. 1, parts being omitted and parts being broken away and in section;

Fig. 3 is an enlarged section corresponding to a section on the line 3-3 of Fig. 2 but showing a modified form of the invention including a turbulence bafiie.

Fig. i is a diagrammatic representation of flow areas in the cross section of the air conduit.

In general the apparatus which exemplifies the invention herein includes a generally flat air conduit is having a top wall l2, bottom wallv l4 and side walls [6 forming a rectangular cross section, a fan it for flowing air through the conduit, a fiber feeding deviceZfl for feeding fibers into the air stream in the conduit, and a screen or condenser 22 moving continuously across the thickness of the conduit for removing the fibers from the air stream in the form of a random laid sheet 24. 7

Three factors are important to the making of uniform fabric in accordance with our invention, (1) the fibers should be fed into the air stream as nearly as possible in the form of individual fibers and not in clumps or groups, and be kept separated as individual fibers until they lodge on the condenser; (2) the distribution of fibers in the direction of movement of the condenser (that is top to bottom of the conduit) need not be uniform, but it is important that it remain con-' stant; (3) the distribution of fibers must be uniform throughout the width of the conduit. The second and third conditions are influenced by the first, and in addition are influenced by conditions of air flow in the conduit. It has been difiicult to achieve all of these conditions, and this invention is concerned with methods and means of accomplishing all three conditions to a high degree.

Individual fiber feed It is always preferred, but especially when using fibers longer than about one half inch, to align the fibers before supplying them to the fiber feeding device 20. One way of accomplishing this is to. form a feed web represented by 26 on one or more standard cards, represented. by 25. Alternatively a number of card slivers can be laid side by side to form a layer which, as a whole, may be led to a feed roll 30 cooperating with a nose plate 32 both of the well known types used with the lickerin of a card. Either the card web or the series of card slivers provides a feed lap of fibers which are predominantly aligned in the direction of the length of the lap and have a minimum of crosswise entanglement. The feed roll, being rotated in any suitable manner, advances these fibers endwise to a combing device which may be, for example, identical with the well known iickerin roll of a card, and is represented by M. This consists of a cylinder from which project a large number of teeth closely spaced and distributed more or less uniformly over the surface. This is usually formed by winding a saw-toothed strip, called a lickerin wire, continuously in a spiral groove covering the surface of the roll.

The combing roll is driven in any suitable manner and at any suitable constant speed which will remove fibers individually from the feed lap. The feed roll advances the fibers endwise into the path of the teeth. The teeth rake or comb the fibers out of the web 26 and feed them into the air stream. This may be accomplished, for example by rotating the cylinder at such speed. (for example 1200 to 5000 R. P. M. for an eight inch diameter) that the fibers are doiied by centrifugal force as soon as they are free of the beard formed by the advancing web 26, and are free of the nose plate.

Feeding the fibers endwise and substantially free of entanglement to the combing roll has the advantage that the individual fibers are combed out of the feed lap without breaking them, and without dragging oth r fibers with them in groups or clumps. This promotes an extraordinarily high degree of fiber separation, and preserves the lengths of the fibers. In previous attempts to feed fibers from unorganized masses such as picker laps, the fibers have been so entangled that they were broken, or removed in clumps, or both. Clumps destroy the uniformity of the fabric being made, and breaking of the fibers into short lengths produces a weak fabric. Likewise the feeding of aligned fibers increases the uniformity across the width of the conduit of the fibers deposited in the air stream and it increases the constancy of the distribution of the fibers from top to bottom of the air stream by increasing the constancy of the rate at which fibers are removed from the beard by the combing roll.

Constant distribution of fibers throughout thickness of conduit Air is drawn axially through the conduit it by the fan :8 and preferably at such a rate that the axial velocity of the air at the point where it passes over the surface of the combing roll is equal to or greater than the peripheral speed of the roll. This avoids windage drag on the fibers being carried by the combing teeth, and causes each individual fiber more or less to fioat in the air stream while resting on a tooth. This facilitates dolfing because it reduces to a minimum, or eliminates entirely, friction between the fiber and the tooth as the fiber tends to slide off the tooth under the action of the centrifugal force. This is particularly important if all the teeth are not perfectly smooth and. polished.

With some types of teeth it is preferable to have the air velocity much higher than the peripheral speed of the combing roll, in order that the fibers may be positively removed from the teeth before the fibers can be carried around the roll out of the air stream. This prevents clogging of the combing roll with fibers.

It is important to have each tooth perfectly clean of fibers before it has passed through the air conduit and is approaching the nose plate to pick up another fiber. Otherwise fibers would accumulate on the teeth and as the teeth became clogged they would comb less and less fibers into the air stream, which would result in immediate thin spots in the fabric, followed by thick spots or clumps as. accumulated. fibers are periodically discharged.

Uniform distribution of fibers across width of conduit When an attempt is made to flow air at certain velocities through a straight, smooth conduit the phenomenon called lamination or skin effect occurs. In this, air separates into layers of dlf-- ferent velocities along the walls of the conduit. Near the wall there frequently occur of air which move slower than the air in the center of the conduit. Frequently these are several layers of difierent velocities, some or which may be substantially zero, and some of which even be in the reverse direction. These latter are called eddy currents. This laminati n causes unequal distribution of fibers across the width of the fabric for several reasons. The slower flow of air near the edges of the conduit deposits fewer fibers on the screen in a given period of time, and thus makes thin edges or selvages on the fabric. Also eddy currents may collect fibers which travel round and round for appreciable periods of time, meanwhile starving the edges, until finally a big clump of fibers beco'n s detached from the eddy and deposits on the screen in the form of a thick spot.

One of the objects of the invention is to avoid lamination and eddy currents, and to this end the invention includes means for stirring up air or creating turbulence which causes currents of air to fiow cyclically transverse to the length oi the conduit, and especially across the width of the conduit, that is, in the direction parallel to the width of the fabric. This turbulence assists in distributing uniformly across the width the fabric the fibers suspended in the air. One example of means for creating this turbulence is illustrated in Fig. 1.

The conduit 10 has an inlet ii of restricted depth or thickness extending uniformly across the width. Adjacent the inlet the conduit has a diffusion chamber represented by the portion between the dotted line &2 and the inlet 5.23. This diilusion chamber is of much greater depth the inlet, to cause the air to have a relatively high velocity in the direction of the length of the conduit (axial velocity) where it passes through the inlet, and a relatively low axial velocity in the diffusion chamber. This sharp increase in the cross section of the conduit, as is known in aerodynamic practice, produc e expansion of the air, resulting in turbulence in the diffusion chamber when the velocity of the air is above a critical low value of the order of a few hundred feet per minute. This turbulence is primarily cyclical or rolling motion of the air in the vertical direction in the conduit. The amplitude of this transverse cyclical motion can be regulated by changing the relative depth of the inlet and depth of the diffusion chamber and the velocity of the air. As shown in Fig. l the diffusion chamber is several times as deep as the inlet, This produces great turbulence or accuses relatively. large transverse motion which initially isvertical... The; air, moving. vertically, strikes the top and; bottom walls of." the conduit,.and is deflected, and so flows in. a. cyclical. or rolling motion across the: width. of.- the conduit. This tends: to result in an axial. flowof: air which. is of: average uniformity across the. width of the conduit, and. prevents lamination of theair: flow, with consequent lack of uniformity.

Turbulence of relatively large magnitude is de: irable in order to completely prevent. lamination of'the fiow at the velocities used. However, this large. magnitude turbulence. produces lacir'of uniformity where considered. on a smaller scale. Consider the. cross section of the conduit to. be divided into relatively large sections: or areas 4d as indicated in Fig. 4. The flow of air axially through each area 44. is. the same as through every other area 4'4, provided the areas selected are large. enough, but if: we consider an area- 4 5 subdivided into smaller areas as at @6- and 48 then the axial flow through one smaller area 46 may not be the same as through a. different, but equal area d8. In order to reduce the size of the areas of uniformity M, the conduit isagain restricted as it approaches the stationv where the fibers are fed into the air stream and in one embodiment of the invention the restriction is such that the thicknessiof the air stream in the zone of introduction of fibers, the zone between the lines 5.!) and 52, is substanti'allythe same as the thickness. of the air stream entering the conduit at inlet. 48.. Thus the thickness of the conduit is gradually reduced from the line 42 to the line 56, thereby increasing the axial velccitz of the air at the point where the fibers are fed into the conduit. This reduction. in the depth of the conduit and the increase in velocity the air stream reduces the magnitude of the transverse movements which are induced by the turbulence, thus in effect compressing the large movements into a number of small amplitude movements and causing a more uniform axial movement of the air, that is the axial movement becomes uniform when averaged over smaller areas d5 and 48.

The fibers are introduced into the air stream this zone of uniformfiow achieved by small iatera-l turbulence and higher velocity, namely in the zone between the lines 58. and 52. Thereafter the air, and its suspended fibers travels uniformly, as regards the width of the. conduit, and deposits fibers uniformly across the width of the screen. It has been found that with some air velocities the impact of the fibers on thescreen is too severe, that is the fibers strike the screen such velocity that they try to pass through the openings of the screen. This results not only in loss of fibers from the fabric, but clogs the sore -11, decreasing its perviousness and reducing the rate at which air can flow through the screen, which in turn makes the fabric thinner. To avoid this result the axial velocity of the air may be decreased after the fibers are entrained, by gradually increasing the depth of the conduit between the line 55 andthe condenser. It has been found that considerable decrease in velocity such as 50% can be achieved without losing the uniformity of fiber distribution which has been efiected by the previous turbulence and uniform combing action. Alternatively the velocity of the air may be sharply induced after passing the lickerin, by rapidly increasing the depth of the conduit, thus increasing the turbulence of the air carrying fibers.

As the velocity of the air at the condenser is decreased, as abmzes suggested. it-is found. that lack of uniformity of thefabric. first begins: to appear asthin. selvases or: lateral edges. is. believed. to. be. due; to. lamination. of; the air now alone the. side, walls. of. the; conduit... due. to air leaving the wall'srather. than. fiowingqsmoothly along; them. Where this. occurs, the condition can: be corrected by placing. baflies; 54, onzthe. side walls;, substantially parallel. to: the selyages; and between the; fiber feed andthe screen, as shown in: Fig... Theebafiles; efiect: reduce the width of th conduit: at; this: point; without. destroying the. predominant: uniformity of width oi; the conduit,-. produce. small eddies. or 10? cal turbulence along the side walls. only- This has. been foundto cause. the air. flowalong: the side walls. tobe uniform with; that the center of thedconduit and. to produce even fabric having even. selvages.

As shown in. Fig. 3 the. bafll'es: are. relatively narrow, for example. of the. order of one to two inches. wide for a. forty inch fabric. They are preferably devoid. of sharp corners, and edges, andare smooth and polished .inorder not: to catch and; hold fibers blowing over them.

We claim as. our invention:

1. The. method. of; forming asubstantially isotropic. layer of fibers which comprises. moving air predominantly in one direction in a relatively thin. and relatively wide; stream, abruptly increasing the thickness: of. the stream uniformly across its width, subsequently restricting the thickness. of the. stream uniformly across its width, moving individual fibers into the air stream adjacent. the restriction and substantial- 1y uniformly" across: its; width, thereafter stopping movement of the fibers while. continuing the. predominantv movement of the air to place the fibers: atv random. in a. webtransverse to said predominantdirection and. continuously removing. the web from the air, stream.

2., The method of. forming a. substantially isotropiclayer of: fibers which comprises moving air predominantly in. one. direction. in a relatively thin. and; relatively wide stream, abruptly increasing the. thicknessv of the stream uniformly across its; width, subsequently restricting the thickness. of. the. stream. uniformly across its width substantially to the original thickness. of the air stream, moving, individual. fibersinto the air siuzeamv adjacent'therestriction and substantially uniformly across its width, thereafter stopping movement of the fibers While continuing the predominant. movement of the air to. place thenbers at, random ina web. transverse to said predominant direction and continuously removing the webfromthe air. stream.

3-. The method of forming a substantially isotropic layer of fibers which comprises moving air predominantly in one direction in a relatively thin andrelatively wide. stream, abruptly increasing the thickness of thestream uniformly across its width, subsequently restricting the thickness of thestream uniformly across. its width, introduties. nd dua fibers; into. the air. stream ad jacent the restriction and substantially uniformly across its width by movement transverse to said predominant direction, thereafter stopping movement of the fibers while continuing the predominant movement of the air to place the fibers at random in a web transverse to predominant direction and continuously removing the web from the air stream.

4. The method of forming a substantially isotropic layer of fibers which comprises moving air predominantly in one direction in a relatively thin and relatively wide stream, abruptly increasing the thickness of the stream uniformly across its width, subsequently restricting the thickness of the stream uniformly across its width, moving individual fibers into the air stream adjacent the restriction and substantially uniformly across its width, thereafter stopping movement of the fibers while continuing the predominant movement of the air to place the fibers at random in a web transverse to said predominant direction and continuously removing the web from the air stream by movement transverse to the width of the air stream and transverse to said predominant direction.

5. The method of forming a substantially isotropic layer of fibers which comprises moving air predominantly in one direction in a relatively thin and relatively wide stream, abruptly increasing the thickness of the stream uniformly across its width, subsequently restricting the thickness of the stream uniformly across its width, moving individual fibers into the air stream adjacent the restriction and substantial- 1y uniformly across its width, again increasing the thickness of the air stream uniformly across its width, thereafter stopping movement of the fibers while continuing the predominant movement of the air to place the fibers at random in a web transverse to said predominant direction and continuously removing the web from the air stream.

6. Apparatus for making continuous fibrous webs comprising in combination an air conduit having a predominant width approximately the width of the web to be made, the conduit having an inlet, means for flowing air through the conduit, the conduit having an abrupt increase in thickness adjacent the inlet for reducing the velocity of the flowing air, and having a reduction in thickness downstream from the expansion for increasing the velocity of the air, means for feeding individual fibers into the air stream substantially uniformly across the width of the conduit where the velocity is so increased, the

conduit having an expansion in thickness downstream from the fiber feeding means for reducing the velocity of the flowing air, a screen across the conduit downstream from the last mentioned expansion for removing fibers from the .3;

air stream and a constriction in width of the conduit between the fiber feeding means and the screen.

7. Apparatus for making continuous fibrous webs comprising in combination an air conduit having a predominant width approximately the width of the web to be made, the conduit having an inlet, means for flowing air through the conduit, the conduit having an abrupt increase in thickness adjacent the inlet for reducing the velocity of the flowing air, and having a reduction in thickness downstream from the expansion for increasing the velocity of the air, means for feeding individual fibers into the air stream substantially uniformly across the width of the conduit where the velocity is so increased, the conduit having an expansion in thickness downstream from the fiber feeding means for reducing the velocity of the flowing air, a screen movable across the thickness of the conduit downstream from the last mentioned expansion for removing fibers from the air stream to form a fabric having selvages, and baffles extending inwardly from the sides of the conduit and being substantially parallel to the selvages and located between the feeding means and the screen.

8. Apparatus for making continuous fibrous webs comprising in combination an a: conduit having a predominant width approximately the width of the web to be made, the conduit having an inlet, means for flowing air through the conduit, the conduit having an abrupt increase in thickness adjacent the inlet for reducing the velocity of the flowing air, and having a, reduction in thickness downstream from the expansion for increasing the velocity of the air, means for feeding individual fibers into the air stream substantially uniformly across the width of the corn duit where the velocity is so increased, a screen across the conduit downstream from the means for feeding individual fibers into the air stream for removing fibers from the air stream, and a constriction in width of the conduit between the fiber feeding means and the screen.

9. Apparatus for making continuous fibrous webs comprising in combination an conduit having a predominant width approximately the width of the web to be made, the conduit having an inlet, means for flowing air through the co duit, the conduit having an abrupt incre thickness adjacent the inlet for reducing the locity of the flowing air, and having a reducti n in thickness downstream from the expansion for increasing the velocity of the air, means for feing individual fibers into the air strea s s stantially uniformly across the width of the conduit where the velocity is so increased, a screen movable across the thickness or" the cond downstream from the means for feeding ind ual fibers into the air stream for removing n, ..s from the air stream to form a fabric havog selvages, and baflies extending inwardly from the sides of the conduit and being substantially parallel to the selvages and located between the feeding means and the screen.

References Cited in the file of this patent UNITED STATES PI'XTZEBTTS Number Name Date 1,584,386 Lindsay 1- May 11, 1928 2,071,438 Shorter et a1. Feb. 193! 2,195,158 Watts Mar. 26, 1940 2,318,243 McClure May l, 1943 2,451,915 Buresh May 1, 1946 2, i60,899 Modigliani et al Feb. :3, 19-h 2,477,675 Wilson et a1 Aug. 2, 1949 FOREIGN PATENTS Number Country Date 688,216 Germany Feb. 15, 1940 

